Asteroid strike map built from nuclear watchdog data

Between 2000 and 2013, 26 asteroids packing at least the energy of 1 kilotonne of TNT hit Earth or exploded in its atmosphere. That's up to 10 times as many as you would expect from existing models of the frequency of asteroid strikes.

These strikes were partially detected by the Comprehensive Nuclear Test Ban Detection Network, which monitors for the covert testing of nuclear weapons. Now the B612 Foundation, which is building the first privately funded asteroid-hunting space telescope, has turned the underlying data into a visualisation.

B612 is releasing the animation today, Earth day, as a call to action on asteroid monitoring. However, it is not clear whether the updated value for the rate of asteroid strikes represents a perceptible increase in the risk these objects pose to Earthlings – since the chance of being hit is still vanishingly small.

The data previously appeared in a 2013 study, which estimated that objects 10 metres wide or larger that could potentially hit Earth are between three and 10 times as common as previously thought.

B612's visualisation maps each explosion on a 3D image of the globe. "We want to dispel the notion in people that asteroid impacts are very rare, when in fact they're not," says B612 Foundation founder and former astronaut Ed Lu. "Nothing brings that home like a visual depiction of the data."

Asteroid diversion?

The largest explosion in the 12 year period was from the 20-metre-wide object that struck Chelyabinsk, Russia last February, which damaged buildings and caused hundreds of injuries, mostly minor ones. That explosion carried as much energy as about 600 kilotonnes of TNT. The smallest explosions were just 1 kilotonne. For comparison, the nuclear bomb dropped on Hiroshima in 1945 was equivalent to approximately 15 kilotonnes.

The B612 Foundation plans to launch a private space telescope called Sentinel, which will scan the sky for these small, dim asteroids that have mostly slipped past our previous observations. Finding them before they hit Earth could allow astronomers to calculate where on the planet they might land and, if they are on a collision course with a major population centre, either deflect them using a spacecraft to change their orbit or blow them up.

"We'll do some good science, but as a side benefit, if anything is about to hit us, we can do something about it," Lu says.

Although these small asteroids may be more common in the solar system than we thought, that doesn't mean the risk of a collision that could wipe out a city has increased, says Peter Brown at the University of Western Ontario in Canada, a co-author of the paper interpreting the data.

"Chelyabinsk caused damage, but didn't destroy the city by any means," he says. "Even if there's a factor of four to five more of those, most of them will fall in the ocean. I would say there's an imperceptible increase to the impact risk."

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